In multi-stage turbine applications, it is known to mount the high and low pressure compressor and turbine stages on co-axial, concentric shafts which may be rotated together or independently during operation of the turbine. Due to the concentric, co-axial arrangement of the shafts, it is frequently rather difficult to gain access to both shafts for the purpose of starting or barring the turbine by rotating fthe shafts with an independent starting or barring motor. The prior art discloses various means by which the high and low pressure stages of such a turbine motor may be started or barred simultaneously by a single auxiliary motor. To achieve this result, various types of clutching devices are known for interconnecting the shafts which mount the high and low pressure stages of the turbine. A difficulty in constructing such clutching devices is to obtain a simple and safe connection during the starting or barring process and yet ensure a safe disconnection during turbine operation, to avoid unintentional engagement of the clutch with attendant inevitable damage to the turbine and clutch.